1. Field of the Invention
The present invention relates to a method for producing a Group III nitride semiconductor light-emitting device whose main surface is a plane other than c-plane, which method realizes improvement of light extraction performance without causing deterioration of crystallinity.
2. Background Art
Patent document 1 discloses a method for producing a GaN crystal layer whose main surface is a non-polar plane (e.g., m-plane or a-plane) or a semi-polar plane (e.g., (11-22) plane) by growing GaN crystal on side surfaces of dents or mesas of an embossed sapphire substrate. Recently, there has been actively developed a Group III nitride semiconductor light-emitting device whose main surface is such a non-polar or semi-polar plane, since such a device is expected to exhibit improved internal quantum efficiency by virtue of increased recombination of electrons and holes resulting from a small internal electric field. In such an embossed sapphire substrate, desirably, dents or mesas are periodically arranged in a stripe pattern as viewed from above, rather than in a dot pattern as viewed from above, from the viewpoints of reduction of variation in crystal orientation of a GaN crystal layer, and improvement of crystallinity.    Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2009-203151
However, when the embossment pattern formed on the sapphire substrate is a stripe pattern, since neither dents nor mesas are provided in the direction of the stripe, light propagated along the stripe on the sapphire substrate does not scatter and may fail to be extracted to the outside.
Meanwhile, when the sapphire substrate has an embossment in which dents or mesas are periodically arranged in a dot pattern as viewed from above, light extraction performance can be improved as compared with the case of a stripe pattern. However, as described above, variation in crystal orientation may be increased, resulting in poor crystallinity.